Effects Of Electron Beam Irradiation And Bacteriostatic Agent On Preservation And Quality Of Crayfish

Crayfish(Procambarus clarkia),has become one of the most important economic freshwater shrimp resources in China.Due to its rich nutrition and high moisture content,it is easily contaminated by microorganisms in the breeding and processing storage environment,resulting in spoilage.In this experiment,steamed crayfish were used as the research object,high-throughput sequencing technology was used to identify the dominant spoilage bacteria in the middle and end stages of shrimp refrigeration,and the bacteriostatic agent was screened by the characteristics of spoilage bacteria,and the fresh-keeping experiment was carried out by combining electron beam irradiation sterilization technology,which was of great significance to extend the shelf life of crayfish and ensure the quality of shrimp meat,and the research content mainly included the following aspects:1.High-throughput sequencing technology was used to identify the microbial composition and dominant spoilage bacteria of cooked crayfish at 4°C and 10°C,analyze and determine the changes of color,texture,pressurized water loss rate,volatile salt-based nitrogen and total number of colonies,and determine the water distribution and migration status of shrimp meat by low-field NMR.The results showed that the main dominant spoilage bacteria in cooked crayfish were Firmicutes,Proteobacteria,Actinobacteriota,bacteroidota and so on.At the same time,the results of highthroughput sequencing showed that the microbial structure of crayfish has been changing during storage.The total number of colonies of steamed crayfish in the storage process showed an upward trend with the extension of time,and the total number of colonies of crayfish exceeded the safety limit of pollution-free aquatic products(6.0(lg(CFU/g))during the limited storage period.At the same time,the L*and a* color values of shrimp meat gradually decreased at storage temperatures of 4 °C and 10 °C,and b* increased,while the elasticity,recovery and chewiness gradually decreased.The water loss rate of shrimp meat under pressure during storage in the 4°C and 10°C groups showed a downward trend.2.Based on high-throughput sequencing,the inhibitory effect of bacteriostatic agents(cinnamic acid,magnolol,polylysine)on dominant putrefying bacteria was analyzed,the minimum inhibitory concentration of bacteriostatic agents on dominant putrefying bacteria was determined,and the effects of bacteriostatic treatment on preservation effect and quality of steamed crayfish were studied.The results show that:The results showed that the inhibitory effect of polylysine was stronger than that of magnolol and cinnamic acid.With the extension of storage time,the quality of crayfish in the two temperature storage groups was consistent.The growth rate of the total colonies of crayfish in the 4℃ storage group was significantly lower than that in the10℃ storage group,which might be due to the increase of the storage temperature of crayfish in the process of refrigeration.Bacterial blooms are related.After 4 days of storage,the total number of colonies in cinnamic acid treatment group and magnolol treatment group was significantly higher than that in polylysine group at 4℃,and after5 days of storage,the total number of colonies in polylysine group was more than 6.0(lg(CFU/g)).3.The changes of color,texture,pressure water loss rate,volatile salt-based nitrogen and total number of colonies were analyzed and determined by using electron beams at different doses(2 and 4 k Gy).The microstructure changes of shrimp meat were observed by fluorescence microscopy,and the changes of volatile odor and composition before and after irradiation of shrimp meat were analyzed by electron nose,gas chromatography and mass spectrometry.The results showed that the irradiation dose of 2 k Gy could extend the shelf life of shrimp meat by 10 days,and the irradiation dose of 4 k Gy could extend the storage period of shrimp meat by 16 days.Electron beam irradiation effectively reduces the microbial load on meat and has excellent potential to improve meat safety and extend shelf life.For the L* and b* values of shrimp meat in the control group and bacteriostatic treatment group,the indexes decreased with the increase of irradiation dose,and the redness value increased by irradiation.The high-dose electron beam destroyed the original dense structure of crayfish muscle fibers,and even fractured,which reduced the meat texture of crayfish,which was consistent with the microstructure of shrimp meat.The main volatile odor components of crayfish are alcohols,aldehydes,ketones,esters,hydrocarbons and nitrogenous compounds,and low-dose electron beam irradiation shrimp meat does not produce adverse sulfide volatile substances during storage.4.Based on the relationship between shrimp freshness index and storage time at different storage temperatures,the Arrhenius kinetic equation was used to establish a shelf life prediction model after freshness of steamed crayfish.The results showed that the relative errors of the predicted value and the measured value of the Arrhenius method of steamed crayfish stored at 2 k Gy and 4 k Gy irradiation doses were 2.00%and 6.86%,respectively,and the relative error of the predicted value and the measured value of the model were within 10%,so it had a high degree of fit,and the quality change and remaining shelf life of electron beam irradiated shrimp meat during storage could be accurately predicted.